Why most of the games are not playable in Windows 10 Mobile ?

I have tried each and every build which Microsoft has released till date in my lumia 535 and my biggest concern is while playing games the screen is not working while trying to tap, i mean the screen resolution is extra wider then the phone display, Aspect ratio is over the screen and that's why the it is not registering my Tap,,, it mostly happened in games like Modern Combat 5, Dungeon Hunter 5, siege fall and other few, But i am able to play few games like Dead Trigger 2, Riptide GP 2, So any one have idea why this is happening.

Games are not optimized for Windows 10 yet. There are a lot of games in the Windows Store that will not scale properly for Windows 10 for Desktop either. Those were initially written for 8.1, and they scale very badly.

Same goes for Mobile. Most of the games that I play are working fine, but a few have issues. Most likely, you're just trying to play more of the ones with issues.